Spray pyrolysis device

Abstract

To provide a spray thermal decomposition device capable of removing nitrogen oxide, without large cost.SOLUTION: A spray thermal decomposition device 10 comprises: a first spray device 3 for spraying mist 2 of a raw material solution into a thermal decomposition furnace 1; one or more combustion burners 4 for thermally decomposing the mist 2 by a combustion gas; and a second spray device 6 for spraying mist 5 of a denitration agent. The combustion burner 4 is arranged so that the combustion gas generates a swirling flow, and the second spray device 6 is installed so as to spray the mist of the denitration agent along a flow direction of the combustion gas or against the flow direction.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a spray pyrolysis apparatus. [Background technology]

[0002] An internal combustion spray pyrolysis device that utilizes the spray pyrolysis method is used as a device for manufacturing fine particles.For example, a raw material solution is sprayed from a nozzle into the inside of a pyrolysis furnace and supplied as a mist (droplets), and the mist is thermally decomposed using combustion gas generated from a combustion burner as a heat source to produce fine particles. On the other hand, it has been reported that in incinerators that perform incineration at high temperatures, the nitrogen content in waste and nitrogen in the air are oxidized during combustion, producing nitrogen oxides (NOx). Because nitrogen oxides are harmful substances, it has been proposed to either install an inlet pipe into the incinerator to inject sodium hydroxide and aqueous ammonia or aqueous urea into the incinerator (Patent Document 1), or to install a denitrification facility outside the incinerator (Patent Document 2), in order to remove nitrogen oxides from the exhaust gas. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-142481 [Patent Document 2] Japanese Patent Application Laid-Open No. 2015-93222 Summary of the Invention [Problem to be solved by the invention]

[0004] There are two types of denitration equipment: dry and wet. In dry systems, the higher the concentration of nitrogen oxides in exhaust gas, the larger the amount of additives and the larger the size of the denitration equipment. On the other hand, in wet systems, nitrogen oxides are captured using water and chemicals, but the higher the concentration of nitrogen oxides, the more water and chemicals are used, resulting in a larger amount of wastewater. In addition, since the wastewater cannot be directly discharged into public watersheds such as rivers, separate treatment facilities are required for the wastewater, and the size of these facilities inevitably increases, resulting in unavoidable increases in costs. Since spray pyrolysis equipment also performs high-temperature treatment in the same way as incinerators, nitrogen oxides are generated inside the pyrolysis furnace. However, installing a denitrification facility to remove the nitrogen oxides would result in excessive manufacturing costs. Therefore, there is a demand for a spray pyrolysis equipment that can remove nitrogen oxides without incurring significant costs. An object of the present invention is to provide a spray pyrolysis apparatus capable of removing nitrogen oxides without requiring a large amount of cost, and a method for producing inorganic oxide particles using the same. [Means for solving the problem]

[0005] As a result of investigations aimed at solving the above-mentioned problems, the inventors have found that by installing a first spraying device for spraying a mist of the raw material solution and a combustion burner for pyrolyzing the mist of the raw material solution within a spray pyrolysis apparatus, and further providing a second spraying device capable of spraying a denitrification agent in a predetermined direction while generating a swirling flow within the pyrolysis furnace using combustion gas generated from the combustion burner, it is possible to efficiently remove nitrogen oxides generated within the pyrolysis furnace without incurring significant costs, while producing inorganic oxide particles without affecting the generation of fine particles.

[0006] That is, the present invention provides the following [1] to

[12] . [1] a first spray device for spraying a mist of a raw material solution into a pyrolysis furnace; One or more combustion burners are arranged so that the combustion gas generates a swirling flow, and the mist is thermally decomposed by the combustion gas. A second spraying device for spraying a mist of denitration agent along or against the flow direction of the combustion gas. A spray pyrolysis apparatus comprising: [2] The spray pyrolysis apparatus according to [1], wherein the second spraying device is provided on the outer periphery of the first spraying device and sprays a mist of the denitrification agent along the flow direction of the combustion gas. [3] The spray pyrolysis apparatus according to [1], wherein the second spray device is provided at the outlet of the pyrolysis furnace and sprays a mist of the denitrification agent in a direction opposite to the flow direction of the combustion gas. [4] The spray pyrolysis apparatus according to [1], wherein the second spray device is provided on the side wall of the pyrolysis furnace and sprays a mist of the denitrification agent in a direction opposite to the flow direction of the combustion gas. [5] The spray pyrolysis apparatus according to [4], wherein the second spray device is installed on the side wall of the pyrolysis furnace so that the angle between the central axis of the spray device and the horizontal direction at the upper end of the second spray device connection part on the inner wall of the pyrolysis furnace is within the range of 5 to 75 degrees. [6] The spray pyrolysis apparatus according to [4] or [5], wherein the second spray device is provided on the side wall of the pyrolysis furnace so that the tip of the second spray device is positioned within a range from the position where the mist sprayed from the first spray device intersects with the inner wall of the pyrolysis furnace on the radial extension of the mist, to a position moved in the vertical direction of the outlet of the pyrolysis furnace at a distance that is less than five times the vertical distance between the outlet end of the first spray device and the intersection position. [7] The spray pyrolysis apparatus according to any one of the above [1] to [6], wherein the denitrification agent is a solution containing one or more selected from urea and ammonia. [8] The spray pyrolysis apparatus according to any one of [1] to [7], wherein the mist sprayed from the second spraying device has an average particle size of 30 μm or less per particle. [9] The spray pyrolysis apparatus according to any one of [1] to [8], wherein the combustion burner is positioned offset from the central axis of the pyrolysis furnace so as to generate a swirling flow of the combustion gas.

[10] The spray pyrolysis apparatus according to any one of the above [1] to [9], wherein the first and second spray devices are fluid nozzles.

[11] A method for producing inorganic oxide particles, comprising the step of spraying a mist of a solution containing a raw inorganic compound from a first sprayer using the spray pyrolysis apparatus described in any one of [1] to

[10] above, and pyrolyzing the mist.

[12] The method for producing inorganic oxide particles according to

[11] above, wherein the raw inorganic compound is one or more selected from aluminum salts, titanium salts, magnesium salts, calcium salts, borates, alkali metal salts, zinc salts, zirconium salts, barium salts, cesium salts, yttrium salts, aluminosilicates, aluminum alkoxides, and silicate alkoxides. [Effects of the Invention]

[0007] The spray pyrolysis apparatus of the present invention is equipped with a second spray device that can spray a mist of a denitrifying agent in a predetermined direction while generating a swirling flow in the pyrolysis furnace using combustion gas generated from a combustion burner, so that it can efficiently remove nitrogen oxides generated in the pyrolysis furnace without incurring significant costs, while producing inorganic oxide particles without affecting the generation of fine particles. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a schematic diagram showing one embodiment of a spray pyrolysis apparatus of the present invention. [Figure 2] FIG. 2 is a schematic diagram showing another embodiment of the spray pyrolysis apparatus of the present invention. [Figure 3] FIG. 2 is a schematic diagram showing another embodiment of the spray pyrolysis apparatus of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same elements are designated by the same reference numerals, and duplicated explanations will be omitted. For convenience of illustration, the dimensional proportions of the drawings do not necessarily correspond to those in the description.

[0010] [First embodiment] FIG. 1 is a schematic diagram showing one embodiment of the spray pyrolysis apparatus of the present invention. The spray pyrolysis apparatus 10 is an internal combustion type, and as shown in Fig. 1, includes a first spray device 3 for spraying a mist 2 of a raw material solution into a pyrolysis furnace 1, and a combustion burner 4 for heating the mist 2 with combustion gas. A second spray device 6 for spraying a mist 5 of a denitration agent along the flow direction of the combustion gas is provided around the outer periphery of the first spray device, and an auxiliary heat source 7 is provided downstream of the mist 2 to promote the denitration reaction of nitrogen oxides produced in the pyrolysis furnace and / or the pyrolysis reaction of the mist.

[0011] (pyrolysis furnace) Any material that is used as a furnace material can be used for the pyrolysis furnace, and the material should be selected taking into consideration the heating temperature, etc. In addition, the inner wall of the metal shell is generally made of firebricks, insulating bricks, castable refractory, etc., either singly or in layers, or in combination. The pyrolysis furnace is preferably in the shape of a vertical cylinder, since this allows a swirling flow to be generated within the pyrolysis furnace. The size of the pyrolysis furnace can be selected appropriately depending on the production scale, but for example, if it is a vertical cylindrical furnace, the inner diameter is preferably 200 to 1600 mm, and the height is preferably 2000 to 30000 mm.

[0012] (spray device) The first and second spray devices can be, for example, fluid nozzles. Examples of fluid nozzles include one-fluid nozzles, two-fluid nozzles, three-fluid nozzles, and four-fluid nozzles. Of these, two-fluid nozzles, three-fluid nozzles, and four-fluid nozzles are preferred. In consideration of heat resistance, the spray devices may be protected by a heat insulating material as needed, or cooling water, cooling air, or the like may be circulated around them.

[0013] Fluid nozzle systems include an internal mixing system in which the gas and the raw material solution are mixed inside the nozzle, and an external mixing system in which the gas and the raw material solution are mixed outside the nozzle, and either system can be employed. The gas supplied to the nozzle can be, for example, air or an inert gas such as nitrogen or argon. Among these, air is preferred from the viewpoint of economy.

[0014] The first spray device may be installed in the center or at the end of the pyrolysis furnace, or above or below the pyrolysis furnace. However, from the viewpoint of preventing the formation of deposits on the pyrolysis furnace wall and allowing the pyrolysis reaction to proceed sufficiently, it is preferable to install it in the approximate center below the pyrolysis furnace. One or more first spray devices may be installed. The spray pyrolysis device shown in FIG. 1 has one first spray device installed in the approximate center below the pyrolysis furnace.

[0015] The installation location of the second spray device is not particularly limited as long as it is located on the outer periphery of the first spray device. For example, it may be near the center or the end of the pyrolysis furnace. However, from the viewpoints of promoting the denitration reaction of nitrogen oxides generated in the pyrolysis furnace, efficiently removing nitrogen oxides, and preventing the denitration agent from adhering to the walls of the pyrolysis furnace, it is preferable to install it adjacent to the first spray device in the approximate center below the pyrolysis furnace. Note that one or more second spray devices can be installed. Note that the spray pyrolysis device shown in FIG. 1 has one second spray device installed adjacent to the first spray device in the approximate center below the pyrolysis furnace.

[0016] The denitration agent is preferably a solution containing one or more selected from urea and ammonia. When the mist of the denitration agent sprayed from the second spraying device contains urea or ammonia, it can decompose nitric oxide and nitrogen dioxide into harmless nitrogen and water through a denitration reaction, for example, as shown in the following formulas (1), (2), (3), and (4).

[0017] 4NO+2(NH2)2CO+O2→ 4N2+4H2O+2CO2(1) 4NO+4NH3+O2→ 4N2+6H2O (2) 6NO2+4(NH2)2CO+4H2O → 7N2+12H2O+4CO2(3) 6NO2+8NH3→ 7N2+12H2O (4)

[0018] The denitration reaction is usually promoted in a temperature range of 700 to 1000°C. Therefore, from the viewpoint of promoting the denitration reaction of nitrogen oxides produced in the pyrolysis furnace and efficiently removing nitrogen oxides, the second sprayer is preferably installed in a position where it can spray a mist of the denitration agent in a region in the pyrolysis furnace where the temperature is 700 to 1000°C. For example, in FIG. 1, the second sprayer may be extended by a pipe or the like and installed downstream of the mist of the raw material solution sprayed from the first sprayer so that the mist of the denitration agent from the second sprayer can be sprayed into a region heated to the above-mentioned temperature by an auxiliary heat source.

[0019] Examples of the solvent for dissolving urea and ammonia include water and organic solvents. The organic solvent can be selected appropriately, and examples thereof include alcohol. Furthermore, a mixture of water and an organic solvent such as alcohol is also suitable for the purpose of suppressing a temperature drop inside the furnace due to the heat of evaporation of water. Among these, water is preferred as the solvent from the viewpoints of environmental impact and production costs. The total content of urea and ammonia in the solution can be set as appropriate, but from the viewpoint of promoting the denitrification reaction of nitrogen oxides produced in the pyrolysis furnace and efficiently removing nitrogen oxides, it is preferably 1% by mass or more and less than 100% by mass, more preferably 5 to 70% by mass, and even more preferably 10 to 50% by mass.

[0020] For example, when a solution containing one or more selected from urea and ammonia is used as the denitrifying agent, the supply amount of the denitrifying agent may be controlled using the total amount of nitric oxide and nitrogen dioxide in the exhaust gas as an indicator so that the ratio of the total number of moles of urea and ammonia in the solution converted into ammonia to the total number of moles of nitric oxide and nitrogen dioxide in the exhaust gas (total number of moles of urea and ammonia converted into ammonia / total number of moles of nitric oxide and nitrogen dioxide) is preferably within a range of 0.2 to 5.0, and more preferably within a range of 1.0 to 4.0.

[0021] The size of the mist of the denitrification agent sprayed from the second sprayer is, from the viewpoint of promoting the denitrification reaction of nitrogen oxides produced in the pyrolysis furnace and efficiently removing nitrogen oxides, preferably 30 μm or less, more preferably 20 μm or less, and even more preferably 10 μm or less, as the average particle diameter per mist. While there is no particular lower limit for the average particle diameter per mist, it is usually 0.1 μm or more, preferably 0.5 μm or more. The average particle diameter of the mist can be adjusted by the shape of the nozzle of the sprayer, the pressure of the gas supplied to the sprayer, and the amount of solution supplied.

[0022] (Combustion burner) The combustion burner is preferably installed offset from the central axis of the pyrolysis furnace so that a strong swirling flow can be generated in the pyrolysis furnace by the combustion gas generated from the combustion burner. By generating a swirling flow, the mist can be retained in the pyrolysis furnace for a distance longer than the length of the pyrolysis furnace, allowing the mist to be heat-treated for a long time and the pyrolysis reaction to proceed sufficiently, and nitrogen oxides also rise while swirling due to the swirling flow, accelerating the denitrification reaction and making them easier to remove. The flow rate of the combustion gas may be adjusted appropriately to generate a swirling flow, for example, 100 to 5000 Nm 3 / h.

[0023] Any combustion burner that is commercially available can be used. The appropriate type of combustion burner should be selected taking into consideration the volume and specifications of the pyrolysis furnace. It is also possible to manufacture a burner according to the specifications of the pyrolysis furnace.

[0024] One or more combustion burners can be installed, and preferably 1 to 4. When multiple combustion burners are installed, the installation positions of the combustion burners do not need to be the same height. In the spray pyrolysis apparatus shown in Figure 1, two combustion burners are installed facing each other on the same circumference, offset from the central axis of the pyrolysis furnace, and a stronger swirling flow advances from the bottom to the top of the pyrolysis furnace, allowing the mist and nitrogen oxides to rise while swirling due to the swirling flow.

[0025] The fuel used in the combustion burner is not particularly limited, but examples thereof include gaseous fuel, liquid fuel, and solid fuel, and two or more of these fuels may be mixed and burned. Examples of gaseous fuels include LPG, city gas, and vaporized organic matter. Examples of liquid fuels include liquefied organic matter such as kerosene, light oil, heavy oil, and recycled oil. Examples of solid fuels include powdered coal, charcoal, and wood.

[0026] The combustion burners are preferably installed so that their flames do not come into direct contact with the mist. This can be achieved by installing the first combustion burner so that its flame does not enter the pyrolysis furnace; for example, by providing a mechanism that can move the combustion burner back and forth and adjusting it as needed. This allows the mist to remain in the pyrolysis furnace for a distance longer than the length of the pyrolysis furnace without coming into direct contact with the flame generated by the combustion burner, thereby allowing the mist to undergo pyrolysis and denitration reactions for a long period of time.

[0027] (auxiliary heat source) The auxiliary heat source is not particularly limited as long as it can provide sufficient heat for the denitrification reaction of nitrogen oxides produced in the pyrolysis furnace and / or the heat required for the pyrolysis reaction of the mist. Examples of the auxiliary heat source include a combustion burner, a hot air heater, and an electric heater. It is preferable to install one or more auxiliary heat sources in order to control the temperature inside the pyrolysis furnace to within the range of 700 to 1000°C. When two or more auxiliary heat sources are installed, they may be arranged facing each other at the same height (on the same circumference) or at different heights and staggered. Note that the spray pyrolysis apparatus shown in Figure 1 has two combustion burners installed as auxiliary heat sources at different heights and staggered.

[0028] From the viewpoint of promoting the denitration reaction of nitrogen oxides produced in the pyrolysis furnace, the auxiliary heat source is preferably installed at a position where the mist of the denitration agent sprayed from the second sprayer can be heated to a temperature of 700 to 1000°C, depending on the installation position of the second sprayer.

[0029] When a combustion burner is used as an auxiliary heat source, it is preferable to install it so that its flame does not come into direct contact with the mist, in order to prevent excessive reaction, melting or deformation of particles, etc. To prevent the flame from the combustion burner from entering the furnace, a mechanism that can move the combustion burner back and forth can be provided, and adjustment can be made according to the length of the flame, etc.

[0030] Second Embodiment FIG. 2 is a schematic diagram showing one embodiment of the spray pyrolysis apparatus of the present invention. 2, the spray pyrolysis apparatus 20 according to this embodiment has a configuration similar to that of the first embodiment, in that it includes a first sprayer 3 for spraying a mist 2 of the raw material solution into the pyrolysis furnace 1, a combustion burner 4 for heating the mist 2 with combustion gas, and an auxiliary heat source 7 for promoting the denitration reaction of nitrogen oxides produced in the pyrolysis furnace and / or the pyrolysis reaction of the mist. However, the spray pyrolysis apparatus 20 according to this embodiment differs in that the second sprayer 6 is provided at the outlet of the pyrolysis furnace 1 to spray a mist 5 of the denitration agent opposite the flow direction of the combustion gas, whereas the spray pyrolysis apparatus 10 according to the first embodiment differs in that the second sprayer 6 is provided on the outer periphery of the first sprayer 3 to spray a mist 5 of the denitration agent along the flow direction of the combustion gas.

[0031] The installation location of the second spray device is not particularly limited as long as it is at the outlet of the pyrolysis furnace, and it may be at the center or end of the outlet. However, from the viewpoint of promoting the denitration reaction of nitrogen oxides generated in the pyrolysis furnace and preventing the denitration agent from adhering to the walls of the pyrolysis furnace, it is preferable to install the second spray device at approximately the center of the outlet. Note that one or more second spray devices can be installed. Note that the spray pyrolysis device shown in Figure 2 has one second spray device installed at approximately the center of the pyrolysis outlet. The second sprayer is preferably installed at a position where it can spray a mist of the denitration agent into a region in the pyrolysis furnace where the temperature is 700 to 1000° C. For example, in Fig. 2, the second sprayer may be extended by a pipe or the like and installed downstream of the mist of the raw material solution sprayed from the first sprayer so that it can spray a mist of the denitration agent from the second sprayer into a region heated to the above-mentioned temperature by an auxiliary heat source.

[0032] The specific configurations of the pyrolysis furnace, the first and second spray devices, the combustion burner, and the auxiliary heat source are as explained in the first embodiment.

[0033] Third Embodiment FIG. 3 is a schematic diagram showing one embodiment of the spray pyrolysis apparatus of the present invention. 3, the spray pyrolysis apparatus 30 according to this embodiment has a configuration similar to that of the first embodiment in that it includes a first sprayer 3 for spraying a mist 2 of the raw material solution into the pyrolysis furnace 1, a combustion burner 4 for heating the mist 2 with combustion gas, and an auxiliary heat source 7 for promoting the denitration reaction of nitrogen oxides produced in the pyrolysis furnace and / or the pyrolysis reaction of the mist. However, the spray pyrolysis apparatus 30 according to this embodiment differs in that the second sprayer 6 is provided on the side wall of the pyrolysis furnace 1 to spray a mist 5 of the denitration agent opposite the flow direction of the combustion gas, whereas the spray pyrolysis apparatus 10 according to the first embodiment differs in that the second sprayer 6 is provided on the outer periphery of the first sprayer 3 to spray a mist 5 of the denitration agent along the flow direction of the combustion gas.

[0034] The installation position of the second spray device is not particularly limited as long as it is installed on the side wall of the pyrolysis furnace where it can spray the denitration agent mist in the direction opposite to the flow direction of the combustion gas, and it may be installed on the side wall of the pyrolysis furnace near the exhaust outlet. However, from the viewpoints of promoting the denitration reaction of nitrogen oxides generated in the pyrolysis furnace, efficiently removing nitrogen oxides, and preventing the denitration agent from adhering to the wall surface of the pyrolysis furnace, it is preferable to install it as follows. That is, as shown in Fig. 3, the second sprayer is preferably installed on the side wall of the pyrolysis furnace so that the angle θ formed between the central axis a of the second sprayer and the horizontal direction b at the upper end of the second sprayer connection part on the inner wall of the pyrolysis furnace is within a range of 5 to 75°. From the viewpoints of promoting the denitrification reaction of nitrogen oxides produced in the pyrolysis furnace and efficiently removing nitrogen oxides, the upper limit of this installation angle is preferably 70° or less, more preferably 65° or less, and even more preferably 50° or less.

[0035] Furthermore, from the viewpoint of promoting the denitrification reaction of nitrogen oxides produced in the pyrolysis furnace and efficiently removing nitrogen oxides, it is preferable to install the second spray device as follows, while controlling the installation angle. The mist of the raw solution sprayed from the first sprayer is usually emitted in a fan shape from the outlet of the first sprayer, with the mist being highest at the vertical center and gradually decreasing in height in the radial direction. The inventors focused on this shape of the mist and found that by providing a second sprayer on the side wall of the pyrolysis furnace so that its tip is positioned on the radial extension c of the mist of the raw solution sprayed from the first sprayer, within a range from the intersection point d with the inner wall of the pyrolysis furnace to a position a specific distance vertically from the outlet of the pyrolysis furnace, the denitration reaction of nitrogen oxides can be further promoted and nitrogen oxides can be removed efficiently. That is, from the viewpoint of promoting the denitrification reaction of nitrogen oxides and efficiently removing nitrogen oxides, it is desirable to provide the second spray device on the side wall of the pyrolysis furnace so that the tip of the second spray device is positioned within a range from the position d where it intersects with the inner wall of the pyrolysis furnace to a position e moved vertically toward the outlet of the pyrolysis furnace, which is preferably 5 times or less, more preferably 4.5 times or less, even more preferably 4 times or less, and especially preferably 2 times or less the vertical distance t between the outlet end o of the first spray device and the intersection position d.

[0036] The specific configurations of the pyrolysis furnace, the first and second spray devices, the combustion burner, and the auxiliary heat source are as explained in the first embodiment.

[0037] The present invention has been described in detail above based on the embodiments. However, the present invention is not limited to the above embodiments. Various modifications of the present invention are possible without departing from the spirit of the present invention. For example, in the above embodiments, a case where one second spray device is installed is described, but the present invention is not limited to this, and two or more second spray devices can be installed by combining the installation modes of the second spray devices described in the above embodiments.

[0038] Furthermore, the spray pyrolysis apparatus of the present invention can be provided with a recovery device and an induced draft fan at the downstream end of the pyrolysis furnace in the direction of mist flow. This allows the generated particles to be moved to the recovery device by the induced draft fan, making it easy to recover the particles. Examples of recovery devices include a bag filter. Alternatively, cooling and recovery may be performed by introducing cooling air into the downstream end of the pyrolysis furnace. Cooling air can be introduced by installing a cooling air intake or by using a fan or blower. These methods may be used at multiple locations. Instead of cooling air, water cooling may be performed, and ion-exchanged water or tap water may be used. Furthermore, a cyclone may be installed upstream of the recovery device to reduce the load on the recovery device and recover coarse particles and foreign matter. Installing a heat exchanger can also utilize residual heat and reduce the amount of exhaust gas. Meanwhile, downstream of the recovery device, dust removal equipment such as a scrubber, desulfurization equipment, denitrification equipment, and other purification equipment may be installed as needed.

[0039] Next, a method for producing inorganic oxide particles using the spray pyrolysis apparatus according to this embodiment will be described. First, a solution containing a raw material inorganic compound is prepared. The solution containing the raw material inorganic compound may be prepared by mixing the raw material inorganic compound and a solvent. The method for mixing the raw material inorganic compound and the solvent may be to add and mix both simultaneously, or to add one to the other, and the mixing method is not particularly limited.

[0040] The raw inorganic compound is not particularly limited as long as it contains elements constituting an inorganic oxide and is soluble in a solvent such as water, and examples thereof include inorganic salts and metal alkoxides. Examples of inorganic salts include aluminum salts, titanium salts, magnesium salts, calcium salts, borates, alkali metal salts, zinc salts, zirconium salts, barium salts, cesium salts, yttrium salts, and aluminosilicates. Examples of metal alkoxides include aluminum alkoxides and silicate alkoxides. One or more types of raw inorganic compounds can be used.

[0041] Examples of aluminum salts include aluminum nitrate, aluminum sulfate, aluminum chloride, aluminum phosphate, aluminum hydroxide, aluminum acetate, and aluminum oxalate. Examples of magnesium salts include magnesium nitrate, magnesium sulfate, magnesium chloride, magnesium phosphate, and magnesium hydroxide. Examples of calcium salts include calcium nitrate, calcium chloride, calcium hydroxide, calcium formate, calcium acetate, and calcium propionate. Examples of borates include metaborates such as boric acid, sodium borate, and potassium borate, tetraborates such as sodium tetraborate and potassium tetraborate, and pentaborates such as sodium pentaborate and potassium pentaborate. Examples of alkali metal salts include lithium carbonate, lithium citrate, lithium chloride, lithium sulfate, lithium hydroxide, sodium carbonate, sodium chloride, sodium bicarbonate, sodium acetate, sodium nitrate, sodium hydroxide, potassium nitrate, potassium chloride, and potassium hydroxide. Examples of calcium hydroxide silicate alkoxides include tetramethyl orthosilicate (TMOS), tetraethyl orthosilicate (TEOS), tetrapropyl orthosilicate (TPOS), and tetrabutoxysilane. Furthermore, solutions in which aluminum oxide or silicon oxide is dispersed in a solvent, and sol solutions of aluminum oxide or silicon oxide can also be used as raw material solutions.

[0042] Among these, as the raw material inorganic compound, from the viewpoint of easily enjoying the effects of the present invention, one or more compounds selected from aluminum salts, titanium salts, magnesium salts, calcium salts, borates, alkali metal salts, zinc salts, zirconium salts, barium salts, cesium salts, yttrium salts, aluminosilicates, aluminum alkoxides, and silicate alkoxides are preferred, one or more compounds selected from aluminum salts, titanium salts, magnesium salts, calcium salts, borates, alkali metal salts, aluminous silicates, aluminum alkoxides, and silicate alkoxides are more preferred, and one or more compounds selected from aluminum salts, magnesium salts, calcium salts, borates, alkali metal salts, and silicate alkoxides are even more preferred.

[0043] Examples of inorganic oxides obtainable from raw inorganic compounds include metal oxides, oxides of alumina, silica, aluminum, and silicon, etc. More specifically, examples include oxides of alumina, silica, aluminum, and silicon, titanium oxide, magnesium oxide, zinc oxide, zirconium oxide, barium oxide, cerium oxide, yttrium oxide, etc., and also include composite oxides that combine these oxides.

[0044] Examples of solvents for dissolving or dispersing the raw material inorganic compounds include water and organic solvents, with water being preferred from the standpoints of environmental impact and production costs.

[0045] The concentration of the raw inorganic compound in the raw inorganic compound-containing solution is preferably 0.01 mol / L to the saturated concentration, more preferably 0.1 to 1.0 mol / L, taking into consideration the density, strength, etc. of the resulting inorganic oxide particles.

[0046] Next, a mist of the raw material inorganic compound-containing solution is sprayed from the first spraying device, whereby the mist is entrained in the flow of combustion gas generated from the first combustion burner, the solvent evaporates from the mist, the mist quickly dries, and the mist is thermally decomposed to produce inorganic oxide particles. The spraying from the first sprayer is preferably carried out while the mist of the denitration agent is being sprayed from the second sprayer. The spraying from the second sprayer may be carried out continuously or intermittently. This allows the denitration agent to decompose and remove the nitrogen oxides produced in the pyrolysis furnace into harmless nitrogen and water.

[0047] Specific embodiments of the first and second spray devices and the denitrification agent are as described above.

[0048] The average particle size of each mist of the raw material solution is preferably 0.5 to 60 μm, more preferably 1 to 20 μm, and even more preferably 1 to 15 μm. The average particle size of the mist can be adjusted by the shape of the nozzle of the spray device and the pressure of the gas supplied to the spray device.

[0049] From the viewpoint of promoting the pyrolysis reaction and the denitration reaction, the temperature inside the pyrolysis furnace is preferably 700 to 1000° C., more preferably 750 to 980° C., and even more preferably 800 to 950° C. If the temperature is less than 700° C., the pyrolysis reaction and the denitration reaction tend to be insufficient, while if the temperature exceeds 1000° C., not only is the denitration reaction insufficient, but particles are also likely to aggregate together.

[0050] Next, the inorganic oxide particles produced by the pyrolysis reaction are transferred from the outlet of the pyrolysis furnace to a recovery device by an induced draft fan and recovered. Examples of recovery devices include a cyclone powder recovery machine and a bag filter. When recovering the inorganic oxide particles, the particle size may be adjusted by passing them through a filter. Furthermore, downstream of the recovery device, dust removal equipment such as a scrubber, desulfurization equipment, denitrification equipment, and other purification equipment may be installed as needed.

[0051] The inorganic oxide particles produced by the method of the present invention may be solid particles, porous particles, hollow particles, or a mixture of two or more of these. Here, in this specification, "solid particles" refers to particles with a structure that does not have an internal cavity, such as particles consisting of a single layer and particles having a core (also called an inner core) and a shell layer (also called an outer shell). Furthermore, "hollow particles" refer to particles with a structure that has an internal cavity (hollow portion) surrounded by an outer shell. The number of cavities may be single or multiple. Furthermore, "porous particles" refer to particles with a large number of through-holes that connect from the particle surface to the interior. The size and shape of the through-holes are not particularly limited. Furthermore, the particles may have closed pores inside.

[0052] The inorganic oxide particles produced by the method of the present invention can have the following properties: The inorganic oxide particles usually have an average circularity of 0.85 or more, preferably 0.90 or more. If the particle shape is nearly spherical, the average circularity will be 0.85 or more. Here, "circularity" is measured by measuring the projected area (A) and perimeter (PM) of a particle from a scanning electron microscope photograph, and if the area of ​​a perfect circle relative to the perimeter (PM) is (B), the circularity of the particle is expressed as A / B. Therefore, the perimeter and area of ​​a perfect circle having the same perimeter as the perimeter (PM) of the sample particle are expressed as PM = 2πr and B = πr, respectively. 2 Therefore, B=π×(PM / 2π) 2 The circularity of this particle is: Circularity = A / B = A × 4π / (PM) 2 The circularity is measured for 100 particles, and the average value is taken as the average circularity.

[0053] The inorganic oxide particles usually have a particle density of 0.1 to 2.5 g / cm 3 and preferably 0.2 to 1.5 g / cm 3 and more preferably 0.3 to 1.0 g / cm 3The particle density can be measured by a gas displacement method in accordance with JIS R 1620. As a particle density measuring device, for example, a dry automatic density meter "AccuPic (manufactured by Shimadzu Corporation)" can be used.

[0054] The inorganic oxide particles have an average particle size of usually 0.5 to 50 μm, preferably 1 to 20 μm, and more preferably 2 to 10 μm. Here, the term "average particle size" as used herein refers to the particle size (d 50 ) As the particle size distribution measuring device, for example, Microtrac (manufactured by Nikkiso Co., Ltd.) can be used. [Example]

[0055] The following examples will explain the present invention in more detail, but the present invention is not limited to the examples below.

[0056] Preparation example Preparation of 10% urea solution 10 kg of urea was added to 90 kg of tap water to prepare 100 kg of 10% urea water. The urea used was manufactured by Kanto Chemical Co., Ltd. (purity 98%, first-class).

[0057] Examples 1 to 10 Using the spray pyrolysis apparatus shown in FIGS. 1 to 3, inorganic oxide particles were produced by the following method. First, 1992 g of tetraethyl orthosilicate, 131 g of aluminum nitrate nonahydrate, 455 g of magnesium nitrate hexahydrate, 516 g of calcium nitrate tetrahydrate, and 1666 g of sodium tetraborate decahydrate were mixed with 100 L of ion-exchanged water and charged into a solution tank and stirred. Next, while a mist of 10% urea water was being sprayed from the second spraying device (two-fluid nozzle) into the pyrolysis furnace, the raw material solution was sent to the first spraying device (two-fluid nozzle) by a liquid feed pump, and the mist of the raw material solution was sprayed into the pyrolysis furnace. The inorganic oxide particles were then collected using a bag filter. Table 1 shows the production conditions for each example, and the type of pyrolysis furnace and the installation position and tip position of the second spraying device are indicated using the following symbols. The size of the reaction section of the pyrolysis furnace was φ200mm x 3000mm, and the combustion burner was offset from the central axis of the pyrolysis furnace so as to generate a swirling flow within the pyrolysis furnace and was installed so that the flame did not come into direct contact with the mist. The angle of the mist (spray angle) of the two-fluid nozzles used as the first and second spray devices was measured indoors in a windless environment at a solution feed rate of 3 kg / h, and was found to be 21°. The average particle size per mist of urea water sprayed from the second spraying device was adjusted by the amount of nozzle air.

[0058] (1) Type of pyrolysis furnace A: One combustion burner (gas burner) is installed below the pyrolysis furnace, and one auxiliary heat source (gas burner) is installed above the furnace. One cooling fan was installed. B: One combustion burner (gas burner) below the pyrolysis furnace, and one auxiliary heat source (electric stove) above. One power supply was installed. (2) Location of the second spray device 1: As shown in FIG. 1, a second spraying device was installed around the periphery of the first spraying device (below the pyrolysis furnace). The nozzle distance between the first and second spray devices was set to 64 mm. did. 2: As shown in FIG. 3, the central axis of the second spray device and the second spray on the inner wall of the pyrolysis furnace The side wall of the pyrolysis furnace is aligned with the horizontal direction at the top end of the device connection so that the angle is as shown in Table 1. A second spray device was installed at 3: As shown in Figure 2, a second spray device was installed at the approximate center of the outlet of the pyrolysis furnace. Ta. (3) Tip position of the second spray device The tip position of the second sprayer is expressed as a multiple of the maximum vertical length of the mist. That is, as shown in FIG. 3, the multiple is based on the intersection point d between the inner wall of the pyrolysis furnace and the radial extension c of the mist of the raw material solution sprayed from the first sprayer. The distance from intersection point d to position e in the vertical direction (upward) of the pyrolysis furnace outlet is expressed as a multiple of the vertical distance t between the upper end o of the first sprayer and intersection point d. For example, in Table 1, a "multiple of vertical distance t" of "0" means that the tip of the second sprayer is at the same height as the intersection point d, and a "multiple of vertical distance t" of "1" means that the tip of the second sprayer is located at the same distance from intersection point d as the vertical distance t between the upper end o of the first sprayer and intersection point d.

[0059] Comparative Example 1 Inorganic oxide particles were produced under the same conditions as in Example 1, except that the mist of 10% urea water was not sprayed from the second spraying device.

[0060] [Table 1]

[0061] The inorganic oxide particles obtained in the examples and comparative examples were subjected to the following analyses, the results of which are shown in Table 2.

[0062] 1.Denitrification rate Using an internal combustion spray pyrolysis device, the combustion burner was burned without spraying the raw material solution or denitrification agent, and the amount of exhaust gas was measured at the outlet of the pyrolysis furnace. The amount of NOx in the exhaust gas was analyzed using an ion chromatograph in accordance with JIS K 0104. The amount of exhaust gas was measured using the Pitot tube method of JIS Z 8808, and the result was 306 m 3 N / h, and the amount of NOx in the exhaust gas was 82 ppm. The denitrification rate was calculated using the following formula.

[0063] Denitrification rate (%)=(82-N) / 82×100 (In the formula, N represents the amount of NOx (ppm) in the exhaust gas measured in the Examples or Comparative Examples.)

[0064] 2.Average circularity The average circularity was measured using the following procedure. That is, the projected area (A) and perimeter (PM) of a particle were measured from a scanning electron microscope photograph, and the area of ​​a perfect circle relative to the perimeter (PM) was defined as (B). The circularity of the particle was expressed as A / B. Therefore, the perimeter and area of ​​a perfect circle with the same perimeter as the perimeter (PM) of the sample particle were calculated as PM = 2πr and B = πr, respectively. 2 Therefore, B=π×(PM / 2π) 2 The circularity of this particle is: Circularity = A / B = A × 4π / (PM) 2 The circularity of 100 particles was measured, and the average value was taken as the average circularity.

[0065] 3.Particle density The density was measured by the constant volume expansion method using a dry automatic density meter (AccuPyc 1340, manufactured by Shimadzu Corporation). That is, after placing the sample in a cell, the cell was filled with an inert gas, and the volume of the sample was measured. The particle density was calculated from this volume and the sample mass measured in advance.

[0066] 4.Average particle size A Microtrac (manufactured by Nikkiso Co., Ltd.) was used as a particle size distribution measuring device to create a volumetric particle size distribution in accordance with JIS R 1629, and the particle diameter (d 50 ) was sought.

[0067] [Table 2]

[0068] Comparing the Examples and Comparative Examples in Table 2, it can be seen that while the exhaust gas discharged from a conventional spray pyrolysis device contained 82 ppm of NOx (Comparative Example 1), by using the spray pyrolysis device of the present invention, the amount of NOx in the exhaust gas can be reduced by up to 80% compared to the conventional spray pyrolysis device (Example 3). Furthermore, the inorganic oxide particles produced using the spray pyrolysis apparatus of the present invention have no difference in physical properties from inorganic oxide particles produced using conventional spray pyrolysis apparatuses and have sufficient performance, which indicates that spraying a denitrification agent into the pyrolysis chamber under specified conditions does not affect the production of inorganic oxide particles. From the above, it can be seen that by using the spray pyrolysis apparatus of the present invention, inorganic oxide particles can be produced while efficiently removing nitrogen oxides generated in the pyrolysis furnace without affecting the production of inorganic oxide particles. [Explanation of symbols]

[0069] 1 Pyrolysis furnace 2 Mist (droplets) of raw material solution 3. First spray device 4 Combustion burner 5. Denitrification agent mist (droplets) 6 Second spray device 7 Auxiliary heat source 10 Spray pyrolysis equipment 20 Spray pyrolysis equipment 30 Spray pyrolysis equipment

Claims

1. a first spraying device for spraying a mist of the raw material solution into the pyrolysis furnace; One or more combustion burners are arranged so that the combustion gas generates a swirling flow, and the mist is thermally decomposed by the combustion gas; a second spraying device for spraying a mist of the denitration agent along or against the flow direction of the combustion gas; A spray pyrolysis apparatus comprising:

2. 2. The spray pyrolysis apparatus according to claim 1, wherein the second spraying device is provided on the outer periphery of the first spraying device and sprays a mist of the denitration agent along the flow direction of the combustion gas.

3. 2. The spray pyrolysis apparatus according to claim 1, wherein the second spray device is provided at an outlet of the pyrolysis furnace and sprays a mist of the denitration agent in a direction opposite to the flow direction of the combustion gas.

4. 2. The spray pyrolysis apparatus according to claim 1, wherein the second spray device is provided on a side wall of the pyrolysis furnace and sprays the mist of the denitration agent in a direction opposite to the flow direction of the combustion gas.

5. The spray pyrolysis apparatus according to claim 4, wherein the second spray device is installed on the side wall of the pyrolysis furnace so that the angle between the central axis of the spray device and the horizontal direction at the upper end of the second spray device connection portion of the inner wall of the pyrolysis furnace is within the range of 5 to 75 degrees.

6. The spray pyrolysis apparatus according to claim 4 or 5, wherein the second spray device is provided on the side wall of the pyrolysis furnace so that the tip of the second spray device is positioned within a range from the radial extension of the mist sprayed from the first spray device, where the mist intersects with the inner wall of the pyrolysis furnace, to a position moved vertically toward the outlet of the pyrolysis furnace, a distance that is less than five times the vertical distance between the outlet side end of the first spray device and the intersection point.

7. The spray pyrolysis apparatus according to any one of claims 1 to 6, wherein the denitrification agent is a solution containing one or more selected from the group consisting of urea and ammonia.

8. 8. The spray pyrolysis apparatus according to claim 1, wherein the mist sprayed from the second spraying device has an average particle size of 30 μm or less.

9. 9. The spray pyrolysis apparatus according to claim 1, wherein the combustion burner is disposed offset from the central axis of the pyrolysis furnace so as to generate a swirling flow of combustion gas.

10. The spray pyrolysis apparatus according to any one of claims 1 to 9, wherein the first and second spray devices are fluid nozzles.

11. A method for producing inorganic oxide particles, comprising the step of spraying a mist of a solution containing a raw inorganic compound from the spray device and pyrolyzing the solution using the spray pyrolysis device according to any one of claims 1 to 10.

12. 12. The method for producing inorganic oxide particles according to claim 11, wherein the raw inorganic compound is one or more selected from aluminum salts, titanium salts, magnesium salts, calcium salts, borates, alkali metal salts, zinc salts, zirconium salts, barium salts, cesium salts, yttrium salts, aluminosilicates, aluminum alkoxides, and silicate alkoxides.

Images